Safety event message transmission timing in dedicated short-range communication (dsrc)

ABSTRACT

Techniques for transmitting vehicle information messages among a plurality of vehicles are disclosed. In an aspect, a transceiver of a vehicle transmits a first set of vehicle information messages over a wireless medium at a first periodic rate, the first set of vehicle information messages including information related to the vehicle. One or more sensors of the vehicle detect an event related to operation of the vehicle. A processor of the vehicle generates a second set of vehicle information messages each including an event flag and information about the event, the event flag indicating that the second set of vehicle information messages is reporting the event. The transceiver of the vehicle transmits a first vehicle safety message of the second set of vehicle information messages over the wireless medium as soon as the first vehicle safety message is generated.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present Application for Patent claims the benefit of U.S.Provisional Application No. 62/206,941, entitled “SAFETY EVENT MESSAGETRANSMISSION TIMING IN DEDICATED SHORT-RANGE COMMUNICATION (DSRC),”filed Aug. 19, 2015, assigned to the assignee hereof, and expresslyincorporated herein by reference in its entirety.

INTRODUCTION

Aspects of this disclosure relate generally to wireless communications,and more particularly to safety event message transmission timing inDedicated Short-Range Communication (DSRC).

Wireless communication systems are widely deployed to provide varioustypes of communication content, such as voice, data, multimedia, and soon. Typical wireless communication systems are multiple-access systemscapable of supporting communication among multiple devices by sharingavailable system resources (e.g., bandwidth, transmit power, etc.).Examples of such multiple-access systems include Code Division MultipleAccess (CDMA) systems, Time Division Multiple Access (TDMA) systems,Frequency Division Multiple Access (FDMA) systems, Orthogonal FrequencyDivision Multiple Access (OFDMA) systems, and others. These systems areoften deployed in conformity with specifications such as 802.11 providedby the Institute of Electrical and Electronics Engineers (IEEE), LongTerm Evolution (LTE) provided by the Third Generation PartnershipProject (3GPP), Ultra Mobile Broadband (UMB) and Evolution DataOptimized (EV-DO) provided by the Third Generation Partnership Project 2(3GPP2), etc.

In the United States, the U.S. Department of Transportation is workingto implement the Dedicated Short-Range Communication (DSRC)communication link to support Intelligent Transportation Systems (ITS)applications, such as wireless communications between high-speedvehicles (Vehicle-to-Vehicle (V2V)) and between vehicles and theroadside infrastructure (Vehicle-to-Infrastructure (V2I)). DSRC can beused for applications such as vehicle safety services, self-drivingfunctionality, commerce transactions via a vehicle, etc.

DSRC uses the Wireless Access for Vehicular Environments (WAVE)protocol, also known as IEEE 802.11p, for V2V and V2I communications.IEEE 802.11p is an approved amendment to the IEEE 802.11 standard andoperates in the licensed ITS band of 5.9 GHz (5.85-5.925 GHz).

In Europe, 802.11p was used as a basis for the ITS-G5 standard,supporting the V2V and V2I communications. The European Commission hasallocated part of the 5.9 GHz band for priority road safety applicationsand V2V and V2I communications. The intention is to ensure compatibilitywith the U.S. even if the allocation is not exactly the same by usingfrequencies that are sufficiently close so that the same antenna andradio transceiver can be used.

SUMMARY

The following presents a simplified summary relating to one or moreaspects disclosed herein. As such, the following summary should not beconsidered an extensive overview relating to all contemplated aspects,nor should the following summary be regarded to identify key or criticalelements relating to all contemplated aspects or to delineate the scopeassociated with any particular aspect. Accordingly, the followingsummary has the sole purpose to present certain concepts relating to oneor more aspects relating to the mechanisms disclosed herein in asimplified form to precede the detailed description presented below.

A method for transmitting vehicle information messages among a pluralityof vehicles includes transmitting, by a transceiver of a vehicle of theplurality of vehicles, a first set of vehicle information messages overa wireless medium at a first periodic rate, the first set of vehicleinformation messages including information related to the vehicle,detecting, by one or more sensors of the vehicle, an event related tooperation of the vehicle, generating, by at least one processor of thevehicle, a second set of vehicle information messages each including anevent flag and information about the event, the event flag indicatingthat the second set of vehicle information messages is reporting theevent, and transmitting, by the transceiver of the vehicle, a firstvehicle information message of the second set of vehicle informationmessages over the wireless medium as soon as the first vehicleinformation message is generated.

An apparatus for transmitting vehicle information messages among aplurality of vehicles includes a transceiver of a vehicle of theplurality of vehicles configured to transmit a first set of vehicleinformation messages over a wireless medium at a first periodic rate,the first set of vehicle information messages including informationrelated to the vehicle, one or more sensors of the vehicle configured todetect an event related to operation of the vehicle, and at least oneprocessor of the vehicle configured to generate a second set of vehicleinformation messages each including an event flag and information aboutthe event, the event flag indicating that the second set of vehicleinformation messages is reporting the event, wherein the transceiver ofthe vehicle is further configured to transmit a first vehicleinformation message of the second set of vehicle information messagesover the wireless medium as soon as the first vehicle informationmessage is generated.

An apparatus for transmitting vehicle information messages among aplurality of vehicles includes means for transmitting configured totransmit a first set of vehicle information messages over a wirelessmedium at a first periodic rate, the first set of vehicle informationmessages including information related to the vehicle, means for sensingconfigured to detect an event related to operation of the vehicle, andmeans for processing configured to generate a second set of vehicleinformation messages each including an event flag and information aboutthe event, the event flag indicating that the second set of vehicleinformation messages is reporting the event, wherein the means fortransmitting is further configured to transmit a first vehicleinformation message of the second set of vehicle information messagesover the wireless medium as soon as the first vehicle informationmessage is generated.

A non-transitory computer-readable medium storing computer executablecode for transmitting vehicle information messages among a plurality ofvehicles includes code to cause a transceiver of a vehicle of theplurality of vehicles to transmit a first set of vehicle informationmessages over a wireless medium at a first periodic rate, the first setof vehicle information messages including information related to thevehicle, cause one or more sensors of the vehicle to report an eventrelated to operation of the vehicle, cause at least one processor of thevehicle to generate a second set of vehicle information messages eachincluding an event flag and information about the event, the event flagindicating that the second set of vehicle information messages isreporting the event, and cause the transceiver of the vehicle totransmit a first vehicle information message of the second set ofvehicle information messages over the wireless medium as soon as thefirst vehicle information message is generated.

Other objects and advantages associated with the aspects disclosedherein will be apparent to those skilled in the art based on theaccompanying drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofvarious aspects of the disclosure and are provided solely forillustration of the aspects and not limitation thereof.

FIG. 1 illustrates an example wireless communication system including avehicle in communication with one or more other vehicles and one or moreroadside access points according to at least one aspect of thedisclosure.

FIG. 2 is a block diagram illustrating various components of anexemplary vehicle according to at least one aspect of the disclosure.

FIG. 3 is a diagram illustrating the conventional timing of Basic SafetyMessage (BSM) transmissions.

FIG. 4 is a diagram illustrating the timing of BSM transmissionsaccording to at least one aspect of the disclosure.

FIG. 5A illustrates various components of the vehicle of FIG. 2 ingreater detail, where the transceiver transmits an event BSM to anothervehicle.

FIG. 5B illustrates the components of vehicle illustrated in FIG. 5A,where the transceiver receives an event BSM from another vehicle.

FIG. 6 illustrates an exemplary flow for transmitting vehicleinformation messages among a plurality of vehicles according to at leastone aspect of the disclosure.

FIG. 7 illustrates an example vehicle apparatus represented as a seriesof interrelated functional modules according to at least one aspect ofthe disclosure.

DETAILED DESCRIPTION

Techniques for transmitting vehicle information messages among aplurality of vehicles are disclosed. In an aspect, a transceiver of avehicle of the plurality of vehicles transmits a first set of vehicleinformation messages over a wireless medium at a first periodic rate,the first set of vehicle information messages including informationrelated to the vehicle. Subsequently, one or more sensors of the vehicledetect an event related to operation of the vehicle. In response, atleast one processor of the vehicle generates a second set of vehicleinformation messages each including an event flag and information aboutthe event, the event flag indicating that the second set of vehicleinformation messages is reporting the event. The transceiver of thevehicle then transmits a first vehicle information message of the secondset of vehicle information messages over the wireless medium as soon asthe first vehicle information message is generated.

These and other aspects of the disclosure are provided in the followingdescription and related drawings directed to various examples providedfor illustration purposes. Alternate aspects may be devised withoutdeparting from the scope of the disclosure. Additionally, well-knownaspects of the disclosure may not be described in detail or may beomitted so as not to obscure more relevant details.

Those of skill in the art will appreciate that the information andsignals described below may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the description below may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof, depending inpart on the particular application, in part on the desired design, inpart on the corresponding technology, etc.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits (e.g., Application Specific Integrated Circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. In addition, for each of theaspects described herein, the corresponding form of any such aspect maybe implemented as, for example, “logic configured to” perform thedescribed action.

As noted in the Background section, in the United States, the U.S.Department of Transportation is working to implement the DedicatedShort-Range Communication (DSRC) communication link to supportIntelligent Transportation Systems (ITS) applications, such as wirelesscommunications between high-speed vehicles (Vehicle-to-Vehicle (V2V))and between vehicles and the roadside infrastructure(Vehicle-to-Infrastructure (V2I)). The DSRC system is being developedwith the aim to require vehicles to transmit short range messages toeach other, informing other vehicles in the vicinity about position,speed, acceleration, heading, and other vehicle data. A vehiclereceiving such messages can warn the driver to avoid potentialcollisions, or in more advanced implementations, can automaticallytrigger an evasive action for that purpose. For example, if anothervehicle is entering an intersection ahead at high speed or approachingin an adjacent lane in a blind spot, the first vehicle will receive V2Vmessages from the other vehicle, enabling the first vehicle to take anynecessary evasive action. As another example, when self-driving(automated) vehicles are driving in close or platoon formation, thesemessages are also used nominally for control. They are part of a tightcontrol loop, where time is critical.

FIG. 1 illustrates an example wireless communication system including avehicle 110 in communication with one or more other vehicles 120 and oneor more roadside access points 140. In the example of FIG. 1, thevehicle 110 may transmit and receive messages with the one or morevehicles 120 and the one or more roadside access points 140 via awireless link 130. The wireless link 130 may operate over acommunication medium of interest, shown by way of example in FIG. 1 asthe medium 132, which may be shared with other communications betweenother vehicles/infrastructure access points, as well as other RATs.

DSRC uses the Wireless Access for Vehicular Environments (WAVE)protocol, also known as IEEE 802.11p, for V2V and V2I communications.IEEE 802.11p is an approved amendment to the IEEE 802.11 standard andoperates in the licensed ITS band of 5.9 GHz (5.85-5.925 GHz) in theU.S. In Europe, IEEE 802.11p operates in the ITS GSA band (5.875-5.905MHz). Other bands may be allocated in other countries. The V2Vcommunications briefly described above occur on the Safety Channel,which in the U.S. is typically a 10 MHz channel that is dedicated to thepurpose of safety. The remainder of the DSRC band (the total bandwidthis 75 MHz) is intended for other services of interest to drivers, suchas road rules, tolling, parking automation, etc. Thus, referring to FIG.1, as a particular example, the medium 132 may correspond to at least aportion of the licensed ITS frequency band of 5.9 GHz.

Communications between the vehicles 110/120 are referred to as V2Vcommunications and communications between the vehicle 110 and the one ormore roadside access point 140 are referred to as V2I communications. Asnoted above, the V2V communications between vehicles 110/120 may includeinformation about the position, speed, acceleration, heading, and othervehicle data of the vehicles 110/120. The V2I information received atthe vehicle 110 from the one or more roadside access points 140 mayinclude road rules, parking automation information, etc.

FIG. 2 is a block diagram illustrating various components of anexemplary vehicle 200, which may correspond to vehicle 110 and/orvehicle 120 in FIG. 1. The vehicle 200 may include at least onetransceiver 204 (e.g., a DSRC transceiver) connected to one or moreantennas 202 for communicating with other network nodes, e.g., othervehicles, infrastructure access points (e.g., the one or more roadsideaccess points 140), etc., via at least one designated radio accesstechnology (RAT), e.g., IEEE 802.11p, over the medium 132. Thetransceiver 204 may be variously configured for transmitting andencoding signals (e.g., messages, indications, information, and so on),and, conversely, for receiving and decoding signals (e.g., messages,indications, information, pilots, and so on) in accordance with thedesignated RAT. As used herein, a “transceiver” may include atransmitter circuit, a receiver circuit, or a combination thereof, butneed not provide both transmit and receive functionalities in alldesigns. For example, a low functionality receiver circuit may beemployed in some designs to reduce costs when providing fullcommunication is not necessary (e.g., a receiver chip or similarcircuitry simply providing low-level sniffing).

The vehicle 200 may also include a satellite positioning service (SPS)receiver 206. The SPS receiver 206 may be connected to the one or moreantennas 202 for receiving satellite signals. The SPS receiver 206 maycomprise any suitable hardware and/or software for receiving andprocessing SPS signals. The SPS receiver 206 requests information andoperations as appropriate from the other systems, and performs thecalculations necessary to determine the vehicle's 200 position usingmeasurements obtained by any suitable SPS algorithm.

One or more sensors 208 may be coupled to a processor 210 to provideinformation related to the state and/or environment of the vehicle 200,such as speed, headlight status, gas mileage, etc. By way of example,the one or more sensors 208 may include an accelerometer (e.g., amicroelectromechanical systems (MEMS) device), a gyroscope, ageomagnetic sensor (e.g., a compass), an altimeter (e.g., a barometricpressure altimeter), etc.

The processor 210 may include one or more microprocessors,microcontrollers, and/or digital signal processors that provideprocessing functions, as well as other calculation and controlfunctionality. The processor 210 may include any form of logic suitablefor performing at least the techniques provided herein.

The processor 210 may also be coupled to a memory 214 for storing dataand software instructions for executing programmed functionality withinthe vehicle 200. The memory 214 may be on-board the processor 210 (e.g.,within the same integrated circuit (IC) package), and/or the memory 214may be external to the processor 210 and functionally coupled over adata bus.

The vehicle 200 may include a user interface 250 that provides anysuitable interface systems, such as a microphone/speaker 252, keypad254, and display 256 that allows user interaction with the vehicle 200.The microphone/speaker 252 provides for voice communication serviceswith the vehicle 200. The keypad 254 comprises any suitable buttons foruser input to the vehicle 200. The display 256 comprises any suitabledisplay, such as, for example, a backlit LCD display, and may furtherinclude a touch screen display for additional user input modes.

In the Safety Channel described above, each vehicle, such as vehicle200, periodically broadcasts the Basic Safety Message (BSM), known alsoin similar systems (e.g., Europe) as the Cooperative Awareness Message(CAM), to provide information about the vehicle. Other systems may alsoexist for providing vehicular safety messages that may or may notimplement the techniques described herein (e.g., China and Japan vehiclemessaging systems). To manage access contention, Enhanced DistributedChannel Access (EDCA), standardized in IEEE 802.11, is used.

BSMs are described in the “Surface Vehicle Standard,” SAE J2735,published by SAE International in 2015, which is incorporated herein inits entirety. Each BSM includes the BSM Part I message and the BSM PartII DF_VehicleSafetyExtension data frames, DF_PathHistory, andDF_PathPrediction. Each BSM includes the BSM Part IIDF_VehicleSafetyExtension data element and DE_EventFlags only as long asan event is active. This data element is not included in a BSM unless atleast one event flag is active, i.e., set to “1.” Each BSM mayoptionally include the BSM Part II DF_VehicleSafetyExtension data frameand DF_RTCMPackage. Table 1 illustrates the data elements (DE) and/ordata fields (DF) that can be transmitted in a BSM.

TABLE 1 BSM Data Elements/Fields Req. Number Data Element/Field BSM PartI DE_DSRCMsgID DE_MsgCount DE_TemporaryID DE_Dsecond DE_LatitudeDE_Longitude DE_Elevation DF_PositionalAccuracy DF_TransmissionAndSpeedDE_Speed DE_TransmissionState DE_Heading DE_SteeringWheelAngleDF_AccelerationSet4Way DE_Acceleration (Longitudinal) DE_Acceleration(Lateral) DE_VerticalAcceleration DE_YawRate DF_BrakeSystemStatusDF_VehicleSize DE_VehicleWidth DE_VehicleLength BSM Part IIDE_EventFlags DF_PathHistory DF_PathPrediction DF_RTCMPackage

Aside from “routine” information about vehicle position and other datacarried in the BSM Part I message, the BSM can transmit informationabout safety related “events” in the BSM Part IIDF_VehicleSafetyExtension data frames, for example, hard brakingactions, that can be used to inform the driver of the receiving vehicleabout the event and/or to allow the receiving vehicle to performautomated operations in response to the event, such as automaticbraking, steering, and/or throttling for collision avoidance. When theDE_EventFlag is not active, the nominal rate at which BSMs are broadcastis 10 Hz (i.e., 10 times per second). When transmitting at the defaultmessage rate of 10 Hz, BSMs are transmitted every 100 ms plus or minus arandom value between 0 and 5 ms. After an initial BSM reporting a safetyevent, i.e., having the DE_EventFlag set to “1,” subsequent BSMs, whichmay still have the DE_EventFlag set to “1” (as a safety event may lastfor several seconds), continue to be transmitted at a nominal rate of 10Hz.

Safety related events are not periodic, and are typically rare.Broadcasting the BSM periodically means that the occurrence a safetyevent will be conveyed to other vehicles with some delay, which can beup to the BSM periodicity of 100 ms nominally, or 50 ms on average. Thatis, because a vehicle typically transmits BSMs 10 times per second,there is a 100 ms gap between BSMs, and thus the longest delay between asafety event and the time it is reported in a BSM is 100 ms. However,because safety events can occur at any point during a 100 ms period, onaverage, a safety event will be reported within 50 ms of occurring.

There are two factors that can increase this nominal delay time. First,in case of Safety Channel congestion (e.g., from a high density ofvehicles in an area), the rate at which BSMs are transmitted isdecreased, thereby increasing the periodicity of the BSMs. The delayscaused by the increased periodicity can double, triple, or more, forexample, from 100 ms to 300 ms or more. Second, EDCA causes some idletime between transmissions, which can range from a few dozenmicroseconds to several milliseconds, depending on the value of theparameters chosen, e.g., the arbitration interframe space number(AIFSN), minimum contention window (CW_(min)), and maximum contentionwindow (CW_(max)).

Conventionally, “routine” BSMs use EDCA parameters of the second highestpriority (i.e., user priority 4 and 5), while BSMs carrying “event”flags (i.e., a BSM with the DE_EventFlag set to “1”) use EDCA parametersof the highest priority (i.e., user priority 6 and 7). Table 2illustrates the EDCA parameter set in IEEE 802.11. In Table 2, AC_BK isthe background access class, AC_BE is the best effort access class,AC_VI is the video access class, and AC_VO is the voice access class.

TABLE 2 EDCA Parameters TXOP Limit User OFDM/CCKOFDM Priority AC CWminCWmax AIFSN PHY 1, 2 AC_BK 15 1023 9 0 0, 3 AC_BE 15 1023 4 0 4, 5 AC_VI7 15 3 0 6, 7 AC_VO 3 7 2 0

Table 3 illustrates only the EDCA parameters CW_(min), CW_(max), andAIFSN for both routine and event BSMs:

TABLE 3 EDCA Parameters for routine and event BSMs Priority CW_(min)CW_(max) AIFSN Routine BSMs 7 15 3 “Event” BSMs 3 7 2

FIG. 3 is a diagram illustrating the conventional timing of BSMtransmissions. The timing diagram illustrated in FIG. 3 begins with ahost vehicle, such as vehicle 200, transmitting a routine BSM at 302 ona shared medium, such as medium 132 in FIG. 1. The host vehicle will nottransmit another BSM for approximately 100 ms (at 304), during whichtime the host vehicle receives BSMs from other nearby vehicles on theshared medium. In FIG. 3, the transmissions on the shared medium fromnearby vehicles are represented by the reference number 310. That is,vehicles both transmit and receive on the same shared medium, orchannel. In the example of FIG. 3, shortly after the host vehicletransmits the first BSM at 302, a safety event occurs at 306. However,the host vehicle must wait until the next BSM opportunity at 304 toreport this safety event.

FIG. 3 also illustrates the timing between routine BSMs from differentvehicles. As shown in call-out 312, transmission of a BSM lasts for 4ms, followed by a gap of (3+(7 to 15)×9)μs before the next BSM istransmitted, where “3” is the AIFSN, “7” is the CW_(min), and “15” isthe CW_(max). In the case of a safety event, however, the gap betweenBSM transmissions is (2+(3 to 7)×9)μs, as shown in call-out 314, where“2” is the AIFSN, “3” is the CW_(min), and “7” is the CW_(max). Thedifference in the length of the gap is due to the event BSMs beingtransmitted using EDCA parameters of the highest priority and routineBSMs being transmitted using EDCA parameters of the second highestpriority.

It would be beneficial to (1) minimize BSM latencies, (2) maximizechannel utilization (and thereby system capacity), and (3) permit higherpriority BSMs (e.g., those indicating “safety events”) to be receivedfaster than “routine” BSMs. Criteria (2) leads to selecting values forthe EDCA parameters that are as low as possible (e.g., the least amountof backoff between transmissions). Criteria (3) has been addressed asdiscussed above by classifying routine BSMs to a lower EDCA priorityclass (e.g., higher values for CW_(min) and CW_(max)), and BSMs carryinginformation on safety events to the highest EDCA priority class.However, as described below, this is not the most optimal design.

Rather, the present disclosure provides a mechanism in whichdifferentiation of latency performance between “routine” BSMs and “highpriority” BSMs carrying safety event flags is not achieved using EDCAparameters, as described above. Using EDCA parameters can make a rathersmall differentiation between the two classes of messages. It alsocarries with it a penalty of lesser channel utilization than isotherwise achievable, since a vast majority of “routine” BSMs havehigher inter-message gaps between them, as illustrated by call-out 312in FIG. 3.

Instead of EDCA parameter differentiation, in the present disclosure, ifa vehicle is experiencing a “safety event,” such as a hard brakingevent, the vehicle does not wait for its nominal transmission slot(e.g., up to 100 ms under non-congested conditions or higher underchannel congested conditions) to transmit the next BSM containing theDE_EventFlag and the DF_VehicleSafetyExtension data frames for theevent. Rather, the vehicle may transmit the event BSM immediately, or assoon as the channel (e.g., medium 132) is available. Alternatively, thevehicle may, for a brief period of time, transmit at some reducedinter-BSM gap (e.g., 50 ms instead of 100 ms), particularly if thechannel is congested and the inter-BSM gap is increased (e.g., above 100ms). In that case, the vehicle resumes normal BSM transmission (e.g.,every 100 ms, or the increased periodicity in the case of channelcongestion) after the event is discontinued, for example, after the hardbraking event ends.

This immediate or near-immediate transmission of event-related BSMs isparticularly relevant when collision avoidance—that is, automatedbraking, steering, and throttling—is invoked. Similarly, because V2V andV2I communication is used for self-driving (automated) vehicles, and therequired latencies are shorter, the near-immediate transmission ofevent-related BSMs is significant. For instance, while driver brakereaction time (i.e., the time from the driver perceiving a “targetvehicle” threat to braking) can exceed one second, and thus theincremental gains in EDCA parameter changes may not be significant wherethe driver remains in control of the vehicle, when vehicles areautomated—and especially when they follow in close or platoonformation—then the immediate or near-immediate transmission ofevent-related BSMs becomes significant. It should be noted that eventhough BSMs are referred to as “safety messages,” for automatedvehicles, these messages are also used for control and are part of atight control loop in which time is critical.

FIG. 4 is a diagram illustrating the timing of BSM transmissionsaccording to at least one aspect of the disclosure. The timing diagramillustrated in FIG. 4 begins with a host vehicle, such as vehicle 200,transmitting a routine BSM at 402 on a shared medium (e.g., medium 132).In the present disclosure, “routine” BSMs are still nominallytransmitted every 100 ms, as described above. Thus, the host vehiclewould not typically transmit another BSM for approximately 100 ms,during which time it receives BSMs from other nearby vehicles on theshared medium. In FIG. 4, the transmissions on the shared medium fromnearby vehicles are represented by the reference number 410. That is,vehicles both transmit and receive on the same shared medium, orchannel.

However, in the example of FIG. 4, shortly after the host vehicletransmits the routine BSM at 402, a safety event occurs at 404. Ratherthan waiting almost 100 ms until the next BSM opportunity to report thissafety event, the host vehicle can transmit an “event” BSM (i.e., a BSMwith the DE_EventFlag set to “1”) at 406 as soon as the channel (e.g.,medium 132) is available. The host vehicle will then resume transmittingBSMs approximately every 100 ms (shown at 408), regardless of whetherthe DE_EventFlag is still set to “1” (which it may be if the safetyevent at 404 is still ongoing at 408). Alternatively, the host vehiclecan transmit the remaining BSMs related to the safety event at a higherfrequency than every 100 ms.

FIG. 4 also illustrates the timing between BSMs from different vehicles.In the present disclosure, all BSMs, whether “routine” or “event”driven, use the highest priority EDCA parameters. Thus, as shown incall-out 412, the gap between routine BSMs is (2+(3 to 7)×9)μs, where“2” is the AIFSN, “3” is the CW_(min), and “7” is the CW_(max).Similarly, as shown in call-out 414, the gap between event BSMs is also(2+(3 to 7)×9)μs.

Note that although the vehicle can wait until the shared medium/channelis available to transmit the BSMs related to a safety event, this is notnecessary. Rather, the vehicle can transmit such BSMs immediately. Ifthe medium is not available, the transmissions may be lost or interferewith other transmissions. To address this issue, the vehicle canretransmit the BSMs related to the safety event some threshold number oftimes (optionally in quick succession) to increase the likelihood thatthey are received by nearby vehicles.

It should be noted that this deviation from the normal message cadencedoes not significantly disrupt the workings of the system, though itdoes result in a small transitional added load on the channel.Considering that safety events, such as hard braking events, are rare,and typically, in a given area and instance, only occur for a smallpercentage of vehicles, this small transitional effect has aninsignificant impact on the timeliness of BSMs from other vehicles.Likewise, from the standpoint of the performance of EDCA, a vehicle thatexperiences a safety event transmits its BSM sooner than its nominalallocated time. However, since transmissions from all vehicles areuniformly distributed in time, the delay experienced by the subjectvehicle due to EDCA is not impacted.

The mechanism of the present disclosure (1) results in better channelutilization and improved DSRC system capacity and (2) considerablyreduces the latency in the safety event triggered BSM received bysurrounding vehicles, giving them more time to react, and therebyreducing the chance of a traffic accident. This reduction of latency canbe 100 ms for the nominal case (i.e., when there is no congestion), upto several hundreds of milliseconds if the channel is congested.

FIG. 5A illustrates various components of the vehicle 200 of FIG. 2 ingreater detail. In the example of FIG. 5A, the processor 210 includes anumber of sub-processors and controllers, specifically, a quick eventprocessor 520, a collision avoidance/obstacle detection processor 522, abrake controller 524, a throttle controller 526, a steering controller528, an automated driving processor 532, a sensor and I/O processor 534,a scene tracking processor 536, a map-based road geometry processor 538,and a target path estimation and selection processor 542 communicativelycoupled via a controller area network (CAN) bus 560.

In the example of FIG. 5A, any or a combination of the sensor(s) 208,the collision avoidance/obstacle detection processor 522, the brakecontroller 524, the throttle controller 526, the steering controller528, the automated driving processor 532, the scene tracking processor536, the map-based road geometry processor 538, and the target pathestimation and selection processor 542 may detect a safety event, suchas a hard braking event, and provide information about the event to thequick event processor 520. The quick event processor 520 may generate anevent BSM including information about the detected safety event and passit to the transceiver 204. The transceiver 204 may immediately, or assoon as the medium 132 is available, transmit the generated event BSM,as described above with reference to FIG. 4.

FIG. 5B illustrates the components of vehicle 200 illustrated in FIG.5A, where the transceiver 204 receives an event BSM from anothervehicle.

The present disclosure features the inclusion of an EDCA-acceleratedQuick Event Flag (QEF), which is event-driven (i.e., generated uponreception of an event BSM) and connects with a quick event processor520. The quick event processor 520 has two functions: to run presetcommands to the brake, throttle and/or steering controllers 524-528 andto inform the collision avoidance/obstacle detection processor 522 andthe automated driving processor 532. This communication bypasses thedelay inherent in the current architecture. Specifically, sending quickevent processor 520 commands to the collision avoidance/obstacledetection and automated driving processors 522 and 532 in addition tothe brake, throttle and/or steering controllers 524-528 allows: (i)emergency or automated vehicle actuation that bypasses the CAN bus 560and (ii) transition to normal operations, since simultaneouscommunication of quick event processor 520 commands to these otherprocessors would enable them to recognize and implement post-eventtrajectory commands after the “safety event” is over.

Referring to FIG. 5B, the transceiver 204 receives a BSM with theDE_EventFlag set to “1.” The transceiver 204 converts the event BSM to aQuick Event Flag and transmits it to the quick event processor 520. Thequick event processor 520 sends preset commands to the brake, throttleand/or steering controllers 524-528 as necessary to react to the safetyevent and informs the collision avoidance/obstacle detection andautomated driving processors 522 and 532 that it did so.

The system illustrated in FIG. 5B is pertinent to vehicles that areequipped with DSRC transceivers, such as transceiver 204, and benefitswill be realized with (i) increasing levels of vehicle drivingautomation, (ii) a growing reliability of the DSRC communications input,(iii) the proliferation of automated collision avoidance and emergencyintervention algorithms, and (iv) the expected advent of self-drivingcars with decreasing following distances and times (e.g., “platooning”or cooperative vehicles).

The modules shown in FIGS. 5A and 5B may be processors coupled to theprocessor 210, Electronic Control Units (ECUs), processes that can beembedded in processor 210 as a system on a chip (SOC), or the like.Alternatively, in certain implementations, these modules may be providedfor or otherwise operatively arranged using other or additionalmechanisms. For example, all or part of the controllers/processors520-542 may be provided in firmware or as software modules stored inmemory 214. Additionally, while in this example thecontrollers/processors 520-542 are illustrated as being separatemodules, it should be recognized that such modules may be combinedtogether as one module or perhaps with other modules, or otherwisefurther divided into a plurality of sub-modules.

FIG. 6 illustrates an exemplary flow for transmitting vehicleinformation messages among a plurality of vehicles according to at leastone aspect of the disclosure. The flow illustrated in FIG. 6 may beperformed by the vehicle 200 of FIGS. 2, 5A, and 5B.

At 602, the transceiver 204 of the vehicle 200 transmits a first set ofvehicle information messages (e.g., BSMs, CAMs, etc.) over a wirelessmedium (e.g., medium 132) at a first periodic rate (e.g., every 100 ms).The first set of vehicle information messages may include informationrelated to the vehicle 200, such as the BSM Part I informationillustrated in Table 1.

At 604, one or more of sensor(s) 208 detect an event related tooperation of the vehicle 200. The event may be a hard braking event, afailure to brake event, an unsignaled lane change event, a failure tofollow a traffic signal event, an excessive speed event, and/or anyevent that may influence the operation of a nearby vehicle (e.g.,safety, heading, speed, etc.).

At 606, a processor of the vehicle 200 (e.g., processor 210 and/or quickevent processor 520) generates a second set of vehicle informationmessages (e.g., BSMs, CAMs) each including an event flag (e.g.,DE_EventFlag set to “1”) and information about the event, such as theBSM Part II information illustrated in Table 1. The event flag mayindicate that the second set of vehicle information messages isreporting the event.

At 608, the transceiver 204 transmits a first vehicle informationmessage of the second set of vehicle information messages over thewireless medium as soon as the first vehicle information message isgenerated.

At 610, the transceiver 204 optionally transmits the remainder of thesecond set of vehicle information messages over the wireless medium atthe first periodic rate. As described herein, the first and second setsof vehicle information messages may be utilized by nearby vehicles forautomated vehicle control for emergency intervention, vehicle-to-vehicle(V2V) and/or vehicle-to-infrastructure (V2I) communication forcoordination with other vehicles in close-following automated vehicleoperation, or any combination thereof.

FIG. 7 illustrates an example vehicle apparatus 700 represented as aseries of interrelated functional modules. A module for transmitting 702may correspond at least in some aspects to, for example, a communicationdevice, such as transceiver 204 in FIG. 2, as discussed herein. A modulefor detecting 704 may correspond at least in some aspects to, forexample, one or more sensors, controllers, or processors, such assensor(s) 208, the collision avoidance/obstacle detection processor 522,the brake controller 524, the throttle controller 526, the steeringcontroller 528, the automated driving processor 532, the sensor and I/Oprocessor 534, the scene tracking processor 536, the map-based roadgeometry processor 538, and the target path estimation and selectionprocessor 542, as discussed herein. A module for generating 706 maycorrespond at least in some aspects to, for example, a processingsystem, such as processor 210 and/or quick event processor 520, asdiscussed herein. A module for transmitting 708 may correspond at leastin some aspects to, for example, a communication device, such astransceiver 204, as discussed herein. An optional module fortransmitting 710 may correspond at least in some aspects to, forexample, a communication device, such as transceiver 204, as discussedherein.

The functionality of the modules of FIG. 7 may be implemented in variousways consistent with the teachings herein. In some designs, thefunctionality of these modules may be implemented as one or moreelectrical components. In some designs, the functionality of theseblocks may be implemented as a processing system including one or moreprocessor components. In some designs, the functionality of thesemodules may be implemented using, for example, at least a portion of oneor more integrated circuits (e.g., an ASIC). As discussed herein, anintegrated circuit may include a processor, software, other relatedcomponents, or some combination thereof. Thus, the functionality ofdifferent modules may be implemented, for example, as different subsetsof an integrated circuit, as different subsets of a set of softwaremodules, or a combination thereof. Also, it will be appreciated that agiven subset (e.g., of an integrated circuit and/or of a set of softwaremodules) may provide at least a portion of the functionality for morethan one module.

In addition, the components and functions represented by FIG. 7, as wellas other components and functions described herein, may be implementedusing any suitable means. Such means also may be implemented, at leastin part, using corresponding structure as taught herein. For example,the components described above in conjunction with the “module for”components of FIG. 7 also may correspond to similarly designated “meansfor” functionality. Thus, in some aspects one or more of such means maybe implemented using one or more of processor components, integratedcircuits, or other suitable structure as taught herein.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not generallylimit the quantity or order of those elements. Rather, thesedesignations may be used herein as a convenient method of distinguishingbetween two or more elements or instances of an element. Thus, areference to first and second elements does not mean that only twoelements may be employed there or that the first element must precedethe second element in some manner. Also, unless stated otherwise a setof elements may comprise one or more elements. In addition, terminologyof the form “at least one of A, B, or C” or “one or more of A, B, or C”or “at least one of the group consisting of A, B, and C” used in thedescription or the claims means “A or B or C or any combination of theseelements.” For example, this terminology may include A, or B, or C, or Aand B, or A and C, or A and B and C, or 2A, or 2B, or 2C, and so on.

In view of the descriptions and explanations above, one skilled in theart will appreciate that the various illustrative logical blocks,modules, circuits, and algorithm steps described in connection with theaspects disclosed herein may be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

Accordingly, it will be appreciated, for example, that an apparatus orany component of an apparatus may be configured to (or made operable toor adapted to) provide functionality as taught herein. This may beachieved, for example: by manufacturing (e.g., fabricating) theapparatus or component so that it will provide the functionality; byprogramming the apparatus or component so that it will provide thefunctionality; or through the use of some other suitable implementationtechnique. As one example, an integrated circuit may be fabricated toprovide the requisite functionality. As another example, an integratedcircuit may be fabricated to support the requisite functionality andthen configured (e.g., via programming) to provide the requisitefunctionality. As yet another example, a processor circuit may executecode to provide the requisite functionality.

Moreover, the methods, sequences, and/or algorithms described inconnection with the aspects disclosed herein may be embodied directly inhardware, in a software module executed by a processor, or in acombination of the two. A software module may reside in Random-AccessMemory (RAM), flash memory, Read-only Memory (ROM), ErasableProgrammable Read-only Memory (EPROM), Electrically ErasableProgrammable Read-only Memory (EEPROM), registers, hard disk, aremovable disk, a CD-ROM, or any other form of storage medium known inthe art, transitory or non-transitory. An exemplary storage medium iscoupled to the processor such that the processor can read informationfrom, and write information to, the storage medium. In the alternative,the storage medium may be integral to the processor (e.g., cachememory).

Accordingly, it will also be appreciated, for example, that certainaspects of the disclosure can include a transitory or non-transitorycomputer-readable medium embodying a method for transmitting vehicleinformation messages among a plurality of vehicles.

While the foregoing disclosure shows various illustrative aspects, itshould be noted that various changes and modifications may be made tothe illustrated examples without departing from the scope defined by theappended claims. The present disclosure is not intended to be limited tothe specifically illustrated examples alone. For example, unlessotherwise noted, the functions, steps, and/or actions of the methodclaims in accordance with the aspects of the disclosure described hereinneed not be performed in any particular order. Furthermore, althoughcertain aspects may be described or claimed in the singular, the pluralis contemplated unless limitation to the singular is explicitly stated.

What is claimed is:
 1. A method for transmitting vehicle informationmessages among a plurality of vehicles, comprising: transmitting, by atransceiver of a vehicle of the plurality of vehicles, a first set ofvehicle information messages over a wireless medium at a first periodicrate, the first set of vehicle information messages includinginformation related to the vehicle; detecting, by one or more sensors ofthe vehicle, an event related to operation of the vehicle; generating,by at least one processor of the vehicle, a second set of vehicleinformation messages each including an event flag and information aboutthe event, the event flag indicating that the second set of vehicleinformation messages is reporting the event; and transmitting, by thetransceiver of the vehicle, a first vehicle information message of thesecond set of vehicle information messages over the wireless medium assoon as the first vehicle information message is generated.
 2. Themethod of claim 1, further comprising: transmitting, by the transceiverof the vehicle, a remainder of the second set of vehicle informationmessages over the wireless medium at the first periodic rate.
 3. Themethod of claim 1, further comprising: transmitting, by the transceiverof the vehicle, a remainder of the second set of vehicle informationmessages over the wireless medium at a higher frequency than the firstperiodic rate.
 4. The method of claim 1, wherein the second set ofvehicle information messages each include the same information about theevent.
 5. The method of claim 1, further comprising: repeatingtransmission of the second set of vehicle information messages up to athreshold number of times to ensure that nearby vehicles receive thesecond set of vehicle information messages.
 6. The method of claim 5,further comprising: updating vehicle state information in the second setof vehicle information messages based on a change in state of thevehicle.
 7. The method of claim 1, wherein a vehicle information messagecomprises a Basic Safety Messages (BSM) or a Cooperative AwarenessMessage (CAM).
 8. The method of claim 1, wherein the information relatedto the vehicle includes a position of the vehicle, an elevation of thevehicle, a position accuracy of the position of the vehicle, a speed ofthe vehicle, a transmission state of the vehicle, a heading state of thevehicle, a steering wheel angle of the vehicle, an acceleration of thevehicle, a brake system status of the vehicle, a size of the vehicle, orany combination thereof.
 9. The method of claim 1, wherein theinformation about the event includes a path history of the vehicle, apath prediction of the vehicle, or any combination thereof.
 10. Themethod of claim 1, wherein the event related to the operation of thevehicle includes a hard braking event, a failure to brake event, anunsignaled lane change event, a failure to follow a traffic signalevent, an excessive speed event, or any combination thereof.
 11. Themethod of claim 1, wherein the first and second sets of vehicleinformation messages are utilized by nearby ones of the plurality ofvehicles for automated vehicle control for emergency intervention,vehicle-to-vehicle (V2V) and/or vehicle-to-infrastructure (V2I)communication for coordination with other vehicles in close-followingautomated vehicle operation, or any combination thereof.
 12. The methodof claim 1, wherein the first periodic rate comprises a periodic rate of100 ms.
 13. The method of claim 1, wherein other vehicles of theplurality of vehicles transmit vehicle information messages on thewireless medium at the first periodic rate.
 14. The method of claim 13,wherein a gap between vehicle information messages transmitted by theplurality of vehicles corresponds to a highest priority access classspecified by Enhanced Distributed Channel Access (EDCA) parameters. 15.The method of claim 1, wherein the plurality of vehicles both transmitand receive vehicle information messages over the same wireless channelof the wireless medium.
 16. The method of claim 1, wherein the wirelessmedium comprises a Dedicated Short-Range Communication (DSRC) wirelesscommunication link in a licensed Intelligent Transportation Systems(ITS) band of 5.9 GHz.
 17. An apparatus for transmitting vehicleinformation messages among a plurality of vehicles, comprising: atransceiver of a vehicle of the plurality of vehicles configured totransmit a first set of vehicle information messages over a wirelessmedium at a first periodic rate, the first set of vehicle informationmessages including information related to the vehicle; one or moresensors of the vehicle configured to detect an event related tooperation of the vehicle; and at least one processor of the vehicleconfigured to generate a second set of vehicle information messages eachincluding an event flag and information about the event, the event flagindicating that the second set of vehicle information messages isreporting the event, wherein the transceiver of the vehicle is furtherconfigured to transmit a first vehicle information message of the secondset of vehicle information messages over the wireless medium as soon asthe first vehicle information message is generated.
 18. The apparatus ofclaim 17, wherein the transceiver of the vehicle is further configuredto transmit a remainder of the second set of vehicle informationmessages over the wireless medium at the first periodic rate.
 19. Theapparatus of claim 17, wherein the transceiver of the vehicle is furtherconfigured to transmit a remainder of the second set of vehicleinformation messages over the wireless medium at a higher frequency thanthe first periodic rate.
 20. The apparatus of claim 17, wherein thesecond set of vehicle information messages each include the sameinformation about the event.
 21. The apparatus of claim 17, wherein thetransceiver of the vehicle is further configured to repeat transmissionof the second set of vehicle information messages up to a thresholdnumber of times to ensure that nearby vehicles receive the second set ofvehicle information messages.
 22. The apparatus of claim 21, wherein theat least one processor is further configured to update vehicle stateinformation in the second set of vehicle information messages based on achange in state of the vehicle.
 23. The apparatus of claim 17, wherein avehicle information message comprises a Basic Safety Messages (BSM) or aCooperative Awareness Message (CAM).
 24. The apparatus of claim 17,wherein the information related to the vehicle includes a position ofthe vehicle, an elevation of the vehicle, a position accuracy of theposition of the vehicle, a speed of the vehicle, a transmission state ofthe vehicle, a heading state of the vehicle, a steering wheel angle ofthe vehicle, an acceleration of the vehicle, a brake system status ofthe vehicle, a size of the vehicle, or any combination thereof.
 25. Theapparatus of claim 17, wherein the information about the event includesa path history of the vehicle, a path prediction of the vehicle, or anycombination thereof.
 26. The apparatus of claim 17, wherein the eventrelated to the operation of the vehicle includes a hard braking event, afailure to brake event, an unsignaled lane change event, a failure tofollow a traffic signal event, an excessive speed event, or anycombination thereof.
 27. The apparatus of claim 17, wherein the firstand second sets of vehicle information messages are utilized by nearbyones of the plurality of vehicles for automated vehicle control foremergency intervention, vehicle-to-vehicle (V2V) and/orvehicle-to-infrastructure (V2I) communication for coordination withother vehicles in close-following automated vehicle operation, or anycombination thereof.
 28. The apparatus of claim 17, wherein the firstperiodic rate comprises a periodic rate of 100 ms.
 29. The apparatus ofclaim 17, wherein other vehicles of the plurality of vehicles transmitvehicle information messages on the wireless medium at the firstperiodic rate.
 30. The apparatus of claim 29, wherein a gap betweenvehicle information messages transmitted by the plurality of vehiclescorresponds to a highest priority access class specified by EnhancedDistributed Channel Access (EDCA) parameters.
 31. The apparatus of claim17, wherein the plurality of vehicles both transmit and receive vehicleinformation messages over the same wireless channel of the wirelessmedium.
 32. The apparatus of claim 17, wherein the wireless mediumcomprises a Dedicated Short-Range Communication (DSRC) wirelesscommunication link in a licensed Intelligent Transportation Systems(ITS) band of 5.9 GHz.
 33. An apparatus for transmitting vehicleinformation messages among a plurality of vehicles, comprising: meansfor transmitting configured to transmit a first set of vehicleinformation messages over a wireless medium at a first periodic rate,the first set of vehicle information messages including informationrelated to the vehicle; means for sensing configured to detect an eventrelated to operation of the vehicle; and means for processing configuredto generate a second set of vehicle information messages each includingan event flag and information about the event, the event flag indicatingthat the second set of vehicle information messages is reporting theevent, wherein the means for transmitting is further configured totransmit a first vehicle information message of the second set ofvehicle information messages over the wireless medium as soon as thefirst vehicle information message is generated.
 34. A non-transitorycomputer-readable medium storing computer executable code fortransmitting vehicle information messages among a plurality of vehicles,comprising code to: cause a transceiver of a vehicle of the plurality ofvehicles to transmit a first set of vehicle information messages over awireless medium at a first periodic rate, the first set of vehicleinformation messages including information related to the vehicle; causeone or more sensors of the vehicle to report an event related tooperation of the vehicle; cause at least one processor of the vehicle togenerate a second set of vehicle information messages each including anevent flag and information about the event, the event flag indicatingthat the second set of vehicle information messages is reporting theevent; and cause the transceiver of the vehicle to transmit a firstvehicle information message of the second set of vehicle informationmessages over the wireless medium as soon as the first vehicleinformation message is generated.